When power is amplified with an amplifier such as a high power amplifier (hereinafter referred to as “HPA”) or the like, desired input-output characteristics may not be obtained due to nonlinear distortion characteristics of the amplifier.
In particular, when the frequency of a radio signal to be amplified is high, it is necessary to perform predistortion for canceling the nonlinear distortion characteristics by using digital signal processing.
For example, Patent Literature 1 discloses a distortion compensation circuit that performs predistortion by using a monitor signal obtained by monitoring an output signal from an amplifier. In Patent Literature 1, the distortion compensation circuit performs the predistortion by using a digital monitor signal. However, the monitor signal obtained by monitoring the output signal from the amplifier is an analog signal (analog monitor signal). In order to generate a digital monitor signal, an analog-to-digital converter (AD converter) performs analog-to-digital conversion on the analog monitor signal.